Death is an experience every culture on earth has to address. It is unknown, and it is frightening because it is the absolute opposite of the most basic part of our existence: life itself.
The way each culture deals with death, however, varies vastly. Celebration might be somber or joyous. Ideas of what comes after includes a variety of ideas including nothing, rebirth, reward and punishment, shallow existence, life as a spirit, and rebirth on another planet.
Death is a highly corrupting event among Zoroastrians. People and places associated with a dead body must be purified. Traditionally, bodies are left to be picked clean by scavenger birds before the bones are buried in a common pit.
The souls of the dead are judged. Those who promoted order and goodness will be rewarded, while the wicked will be cleansed by fire, a highly purifying element in Zoroastrianism.
Raelians are atheists who have no beliefs in a supernatural world. However, they still have afterlife beliefs. The worthy will be uploaded into cloned bodies. In its early days, aliens known as Elohim would do the judgment, and the next life would be on a paradise planet. Now the idea is that humanity will develop cloning technology and recreate selected souls here.
Raelians have a piece of bone removed from the skull at death in order to provide DNA material to be used in the cloning process.
Scientologists believe the thetan, which roughly corresponds to the concept of a soul, moves from body too body through reincarnation. Through each life the thetan can pick up or shed harmful engrams which limit the thetan's potential. The goal of Scientology is to eliminate engrams and develop the thetan until it no longer needs a body to interact with the world.
No ceremonies are necessary for reincarnation, so funerals are focused on celebrating the deceased's life and allowing survivors to come to terms with the passing.
Groups which eventually embrace mass suicide have a variety of beliefs about what comes next. What unites them is their reasoning for suicide, which is generally escape from some fate they consider worse than death.
For those at Jonestown, suicide was an escape from capitalist forces that threatened to take away their communal way of life.
For David Koresh, death avoided capture by the agents of Satan, who populate the world and run governments, including the law enforcement agencies that laid siege to their compound in Waco, Texas.
For Heaven's Gate, suicide allowed believers to migrate their souls to a spaceship before the impending recycling of the earth and its inhabitants.